The use of fiber optic technology in the communications industry continues to increase. Fiber optic communications provide numerous advantages such as increased bandwidth, less noise, lower signal-to-noise ratio requirements, and lower error rates. In addition, the use of fiber optic cable relative to metallic conductors permits a much larger traffic of communication to occupy the same space previously required by metallic conductors.
As known in the art, communication of signals through an optic fiber is accomplished by placing communications circuitry at the tips of both ends of the optic fiber. For purposes of this document, such communications circuitry includes "photonic devices", that is, devices for conversion of signals between electrical and optical media. FIG. 1a illustrates a perspective view of certain components of such a system. Specifically, FIG. 1a illustrates a perspective and cut-away view of a prior art fiber optics package 10. Package 10 is typically a parallelepiped in shape, having a length on the order of 1.0 inches and a width and height on the order 0.75 inches.
Package 10 is typically constructed of Kovar and houses various components. These components, as described in greater detail below, are commonly disposed through the top of package 10, thereby providing limited access to the components once they are affixed within the interior of package 10. After the components are properly installed within package 10, a top (not shown) is sealed to the package by a known resistive seam weld process, thereby hermetically sealing the components from contaminants exterior to package 10.
A ferrule 12 is attached to package 10 and permits access through a hole or "pass-through" in one side of package 10. Typically, ferrule 12 is 0.200 inches in length and 0.125 inches in the outside diameter. An optic fiber 14 extends from a sleeve 16. Optic fiber is on the order of 0.005 inches in diameter, and extends a length of 0.500 inches from sleeve 16. As described in greater detail below, optic fiber 14 is fitted through ferrule 12. Consequently, the tip 18 of fiber 14 may be fixed in position with respect to circuitry within package 10. Although sleeve 16 is shown in a cut-away view, it should be understood that it (or a lesser protective layer such as a buffer coating) extends for a length typically on the order of 1.0 meters outward of package 10.
With reference to the interior of package 10, a thermal electric cooler 20 is affixed to the bottom of package 10. Thermal electric cooler 20 supports, via a deposit of solder (not shown), a carrier 22. Carrier 22 supports various components known in the art. For example, carrier 22 supports a thermistor 24 and a backwave detector 26. Carrier 22 also supports a U-shaped subcarrier 28. A submount 30 is disposed on top of subcarrier 28 and supports a laser 32. Laser 32 communicates signals to tip 18 of fiber 14 (once fiber 14 is correctly positioned with respect to laser 32). While FIG. 1a illustrates a transmitter (i.e., laser 32), it should be understood that a receiving device, such as a photodiode, could be included as an alternative. Moreover, the circuitry for communicating to/from the fiber could be a transceiving device as well.
Carrier 22 further includes an integral extension 34 which supports an adjustment post 36. A portion of solder (not shown) is disposed on the top 38 of adjustment post 36 to support a retaining slab 40 (shown in FIG. 1a outside package 10 and proximate fiber 14). Retaining slab 40 includes a longitudinal groove 42 which, as described in greater detail below, retains optic fiber 14 in a fixed position with respect to laser 32.
Package 10 also houses an integrated circuit 44 which connects in various manners to the componentry of carrier 22, and also to a series of package pins 46. A pair of power conductors 48 are connected to respective power pins 50. Thus, signal interaction to the communications circuitry, and power supply to thermal electric cooler 20, may be accomplished external from package 10 by accessing pins 46 and 50.
FIG. 1b illustrates package 10 of FIG. 1a with optic fiber 14 affixed in place with respect to the communications circuitry housed by package 10. Specifically, as appreciated from FIG. 1b, sleeve 16 is fitted through ferrule 12 such that fiber 14 extends inward within package 10. Fiber 14 is affixed within groove 42 of retaining slab 40 by use of solder (for metalized fiber) or epoxies (typically for a non-metalized fiber). Specifically, either of these materials are used to form deposits 52 and 54 along slab 40. In addition, a solder deposit 56 is formed between ferrule 12 and sleeve 16 to prohibit contaminants from passing between the two components and into the interior of package 10.
Once fiber 14 is affixed to slab 40, slab 40 is placed in contact with the solder deposit formed on top 38 (see FIG. 1a) of adjustment post 36. Particularly, slab 40 is situated to position the tip 18 of fiber 14 in a precise position with respect to laser 32. As is known in the art, typically the tolerance for locating tip 18 is on the order of 0.1 to 2.0 microns. Having located slab 40 in place, heat is applied to cause the solder between it and adjustment post 36 to flow. Thereafter, the solder is permitted to cool, thereby affixing slab 40 and fiber tip 18 in place. Typically, signal measurements are then made through fiber 14 to ensure that it is affixed within proper tolerance and is communicating effectively with laser 32. If outside the acceptable tolerance, the solder is reheated and the process is performed again until acceptable tolerances are met.
From the above, it may be appreciated that the prior art requires performance of incredibly complicated and delicate procedures within the confines of package 10 to properly position the optic fiber tip 18 in place with respect to laser 32. As stated above, package 10 is typically on the order of 1.0 inches in length and 0.75 inches in width. Consequently, the complexities of affixing the optic fiber in place are vastly increased because of the spatial limitation imposed by package 10. Further, the processes described above often require manipulation of various tools such as probes, lasers and tweezers within the tiny area created by the top-access of package 10. These limitations not only lengthen the task, but increase the opportunity to damage any of the various components within package 10 while completing the affixation process.
It is therefore an object of the present invention to provide a method and apparatus for precisely affixing an optic fiber tip in position with respect to a fiber communications circuit outside of the fiber optics package.
It is further object of the present invention to provide such a method and apparatus for reducing the possibility of damage to the optic fiber while installing it in a fiber optics package.
It is a further object of the present invention to provide such a method and apparatus for reducing the possibility of dislodging the mechanism retaining the optic fiber in place while installing it in a fiber optics package.
It is a further object of the present invention to provide such a method and apparatus for providing an inventory of individual optic fibers fixed in position with respect to respective communications circuits, but readily available for insertion into various different types of fiber optics packages.
Still other objects and advantages of the present invention will become apparent to those of ordinary skill in the art having reference to the following specification together with its drawings.